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ASE Automobile & Light Truck (A1–A8) — Practice Exam

A8 Emissions: practice questions

Our ASE A1–A8 bank has 8 questions on this topic. Here are 4 of them with answers; the full mock exam draws from every topic, like the real one.

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Question 1 · A8 Engine Performance

What tool helps find small EVAP leaks?

  1. A smoke machine
  2. A compression gauge
  3. A refractometer
  4. A timing light
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A. A smoke machine — Smoke appears at the leak.

Question 2 · A8 Engine Performance

What does the EGR system reduce?

  1. Carbon monoxide (CO) and hydrocarbons
  2. Hydrocarbons only
  3. Oxides of nitrogen (NOx)
  4. Carbon dioxide (CO2)
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C. Oxides of nitrogen (NOx) — It lowers combustion temperature.

Question 3 · A8 Engine Performance

How does the PCM monitor catalytic converter efficiency?

  1. By measuring back pressure
  2. By counting misfires
  3. By comparing upstream and downstream oxygen sensor signals
  4. By measuring exhaust temperature only, before and after the converter, during cruise
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C. By comparing upstream and downstream oxygen sensor signals — A good converter flattens the downstream sensor signal.

Question 4 · A8 Engine Performance

What does the EVAP system do?

  1. Pumps fuel to the injectors
  2. Recirculates exhaust gas into the intake to lower combustion temperatures
  3. Stores fuel vapors and routes them to the engine to be burned
  4. Cools the exhaust
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C. Stores fuel vapors and routes them to the engine to be burned — A loose gas cap is a common cause of EVAP codes.

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